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https://issues.apache.org/jira/browse/MAPREDUCE-5124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16245754#comment-16245754
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Peter Bacsko commented on MAPREDUCE-5124:
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Hm, I believe there's a race condition in my previous patch.
1. Task attempt invokes setNextStatusUpdate() via RPC
2. This results in attempt.needStatusUpdate = true
3. However, an update for the same attempt is already running, setting
needStatusUpdate = false at the end
4. New event is queued
5. New event is taken from the queue, updater logic runs
6. Updater logic sees that needStatusUpdate = false -- an update is lost
I'll re-think this and update the patch.
> AM lacks flow control for task events
> -------------------------------------
>
> Key: MAPREDUCE-5124
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5124
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mr-am
> Affects Versions: 2.0.3-alpha, 0.23.5
> Reporter: Jason Lowe
> Assignee: Peter Bacsko
> Attachments: MAPREDUCE-5124-CoalescingPOC-1.patch,
> MAPREDUCE-5124-proto.2.txt, MAPREDUCE-5124-prototype.txt
>
>
> The AM does not have any flow control to limit the incoming rate of events
> from tasks. If the AM is unable to keep pace with the rate of incoming
> events for a sufficient period of time then it will eventually exhaust the
> heap and crash. MAPREDUCE-5043 addressed a major bottleneck for event
> processing, but the AM could still get behind if it's starved for CPU and/or
> handling a very large job with tens of thousands of active tasks.
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